The present invention relates to lapping machines and methods in general and more particularly to a machine and method for lapping a hard metallic surface on a lap plate charged with an abrasive compound.
A multiplicity of tools used on machine tools for cutting, piercing, etc. have flat surfaces which must be ground and subsequently finish lapped to a high degree of surface finish and flatness. Example of such tools are punches, die plates, gages, etc. The surfaces to be lapped are generally very hard as being composed of hardened tool steels, carbides and the like. Lapping is effected on a lap in the form of a plate, for example, of cast iron, having a precisely flat surface loaded with an abrasive compound such as diamond, silicon carbide, fused alumina or boron carbide powder for example. A "vehicle" or binder, in the form of an oil or grease base lubricant is used for wetting and lubricating the surface being lapped, the surface of the lap plate and the abrasive particles. Lapping of a workpiece surface is effected by rubbing the surface to be lapped in engagement with the abrasive-loaded lap plate, back and forth in a regular motion, in an orbiting motion, in a figure eight motion, or in a circular motion.
Lapping may be effected manually, which requires considerable skill and experience on the part of the worker, or it may be effected by means of power operated apparatus or machines. Whatever the method used for lapping a workpiece surface, it is a delicate and slow operation. Care must be taken to utilize evenly all of the surface of the lap plate, and to avoid lapping constantly over the same areas of the lap plate, thus causing uneven wear of the surface which in turn defeats entirely the results sought to be accomplished by lapping a surface to a high finish and an accurate flatness.